JPH0596648A - Conductive multilayer tube - Google Patents

Abstract

(57) [Summary] [Objective] To provide a conductive multi-layer tube in which the change in conductivity due to the environment is small. [Structure] The present invention comprises an organic polymer material as a main component.
In a conductive multi-layer tube having a multi-layer structure of at least two layers, at least two layers formed by gradually reducing the content of the conductive agent in each layer from the inner surface layer to the outer surface layer It is the above multilayer tube. With such a configuration, variations in electric resistance in each layer, electric resistance due to environmental changes can be reduced, and improvement in withstand voltage can be expected,
Furthermore, since the conductive agent content is smaller in the multilayer and surface layer, the bleed-out of the softening agent from the roll is reduced even when applied to a roll having a conductive elastic body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive multi-layer tube whose conductivity (resistivity) changes little with the environment.

[0002]

2. Description of the Related Art Conventionally, as a conductive elastic roll or the like used as a charging roll of an electrophotographic copying machine or the like, at least a roll having a conductive elastic layer on its surface contains a conductive agent such as carbon. Some of them were found to be coated with a conductive tube.

As a charging system, a contact charging system using a charging roll and a corona discharging system using a corona charger without using the charging roll are generally used.

However, the corona discharge method is 5 to 10
Since a high voltage of KV is applied, there is a problem in operability, and ozone generated by the discharge is also problematic in terms of work environment pollution and hygiene. Further, in terms of performance, there are drawbacks such as uneven charging and poor charging efficiency. Therefore, at present, the contact charging method is not yet the mainstream, but the corona discharge method tends to change to the contact charging method.

[0005]

However, a conventional electrically conductive tube-coated charging roll, for example, is
When the photoconductor is charged by the contact charging method, there are many cases where the photoconductor is not uniformly charged and a clear image cannot be obtained due to the large variation in resistance and the change in resistance due to the environment. Dielectric breakdown is likely to occur due to the conductive agent, and there is a tendency that it is difficult to obtain a suitable image due to reduction in withstand voltage, bleeding out of the softening agent from the elastic layer of the roll, and the like.

The present inventors have conducted various studies to obtain a conductive tube suitable for coating a roll or the like by solving the above-mentioned problems of the conventional charging roll using the conductive tube. The present invention has been reached.

[0007]

The present invention relates to a conductive tube having a multilayer structure of two or more layers containing an organic polymer material as a main component, and the content of the conductive agent in each layer is changed from the inner surface layer to the surface layer. A multi-layer tube having at least two layers, which are mixed by gradually decreasing the size from large to small, wherein the inner surface layer has the maximum conductivity and the surface layer has the minimum conductivity layer. Regarding tubes.

Such a tube has a multi-layered structure having at least two layers, and the conductive agent contents of the respective layers in the film thickness direction are different stepwise, and are gradually decreased toward the surface layer. Is desirable. At this time, the total content of the conductive agent in the tube is 10% by weight to 5%.
It is desirable that the compounding amount be 0% by weight, preferably 10% by weight to 30% by weight <, and if the amount is out of this range, the present invention may not be sufficiently effective, but this value is not always required. However, if necessary, the content may be other than the above value. In this case, it is needless to say that the category described as stepwise includes an inclined configuration.

Although the content of the conductive agent in the inner surface layer is not particularly limited, it is preferably 10 to 30% by weight, and when the content is less than 10% by weight, the desired conductivity cannot be obtained. In many cases, it is not preferable because the physical properties are impaired, but other than this value can be used depending on the application. Further, the conductive agent content of the surface layer is gradually reduced from the inner surface, may be not contained at all, or may contain a required amount less than the inner surface,
The content is not particularly limited, but preferably 2 to 10
For example, it can be about% by weight. At this time, if necessary, one or more intermediate layers may be provided between the surface layer and the inner surface layer, and the content of the conductive agent in the intermediate layer may be an intermediate amount between the surface layer and the inner surface layer. Good. At this time, when two or more intermediate layers are provided, the amount of the conductive agent is gradually reduced from the layer arranged on the inner surface side to the layer arranged on the surface layer side so as to decrease from large to small. It is desirable to be strict.

The inner surface layer and the surface layer may be made of different resins, and the intermediate layer provided if necessary may be a resin layer having a mixture of both resins. In this case, it is preferable that the mixed constitution is such that the content of the resin constituting the inner surface is gradually reduced from the inner surface layer to the surface layer, but the present invention is not particularly limited to this.

Further, in order to protect the conductive multi-layer tube, a protective layer may be further provided on the surface layer as an outermost layer, and the outermost layer is mainly composed of an organic polymer material containing no conductive agent. However, if necessary, an appropriate filler may be contained, and there is no particular limitation on this.

For example, when a roll having a conductive elastic layer is coated with the conductive multi-layer tube having the above-mentioned structure, and when the roll is used as a charging roll by a contact charging system, the photoreceptor is charged by the charging roll. Also,
The tube has less variation in resistance in each layer and resistance change due to the environment, and the withstand voltage is improved, so that the charging roll using such a tube can uniformly charge the photoconductor and the like. Thus, it is possible to obtain a good image. In addition, such a charging roll can prevent bleed-out from the elastic layer in the roll and also provide good interlayer adhesion. The reason why bleed-out can be prevented is that since the coating tube of a conventional charging roll is a single layer, the conductive agent is evenly distributed, so the softening agent in the elastic body passes through the conductive agent in the tube to the outer surface. Although bleeding out has occurred, the tube of the present invention is multi-layered, and because the content of the conductive agent is smaller in the surface layer, the bleeding out through the conductive agent is blocked by the surface layer and it is difficult to bleed out to the outer surface. by. Therefore, to further prevent bleed-out,
It is more desirable to further provide a protective layer containing no conductive agent on the surface layer.

Examples of the organic polymer material forming the conductive multilayer tube of the present invention include various thermoplastic elastomers, polycarbonates, polyesters, polyarylates,
Thermoplastic resins such as polyphenylene sulphite, polyamide, polysulfone, polyparabanic acid, fluorine resin, polyvinyl chloride, polystyrene, thermoplastic polyimide resin and polyurethane (polyester type, polyether type) and copolymers derived from them. , A mixture and the like can also be exemplified, but other than this, it suffices to select and use an appropriate one such as a thermosetting resin, which is not particularly limited.
Rather, those that can be extruded are often used favorably.

As the conductive agent according to the present invention, conductive carbon black, for example, carbon black such as acetylene black and Ketjen black (conductive furnace black type) can be exemplified as preferable ones, but not limited thereto and metal Any powder, metal oxide such as tin oxide, indium oxide, or any other material having conductivity may be used, and there is no particular limitation. Further, if necessary, stabilizers, lubricants, pigments, dyes, UV inhibitors, fillers, other various resins and the like may be added and are not particularly limited.

In order to form the conductive multi-layer tube of the present invention, a method in which an annular die is attached to a plurality of extruders and the film is formed by co-extrusion is preferably a seamless tube.
Other flat plate co-extrusion methods, or a plurality of films having different conductive agent contents are formed and laminated by an appropriate method such as a pressure bonding method or a dry laminating method so that the conductive agent content changes stepwise. The multilayer film may be used to form a tube, and there is no particular limitation, and the multilayer tube may be formed by centrifugal molding or another method.

Stretching and / or heat treatment of the conductive multilayer tubular film of the present invention is carried out as necessary and is not particularly limited, and the method is an appropriate method such as a commonly used tubular method or tenter method. However, the present invention is not limited to this. Further, it may be stretched so as to have a heat shrinkability, and may be used as a shrink tube. At this time, the heat shrinkage rate is not particularly limited and may be set to an appropriate value as necessary, and is usually 0 to 10% in the axial direction and 10 to 10 in the circumferential direction.
A value of about 80% can be exemplified.

When a protective layer is required, the conductive multi-layer tube of the present invention may have a thickness of 5 to 50 μm, more preferably 10 to 30 μm. If it is 50 μm or more, the protective layer has a large resistance value. However, there are no particular restrictions on such values. The surface layer is 1
The thickness of the inner surface layer is preferably 0 to 200 μm and the thickness of the inner surface layer is preferably 30 to 200 μm.

The conductive multi-layer tube of the present invention is preferably used as a roll-coated tube such as a roll-up tube for primary charging, transfer, static elimination, etc., such as electrophotographic copying machines. The present invention is not limited to the above, and can be widely used for other applications, and it can be expected to be expanded in the future.
In the case of a roll-coated tube, the roll and the tube may be coated via an appropriate adhesive substance, or may be directly coated without using an adhesive substance (may be used if necessary). In many cases, it is often preferable to use a heat-shrinkable shrink tube.

The present invention will be described below with reference to examples.

[0020]

【Example】

Example 1 Three extruders were equipped with circular co-extrusion dies, and urethane resin was the main component, and the Ketjen black content in each layer was 15% by weight, 10% by weight, 5% by weight and the inner surface From the above, the composition in which the surface layers were compounded in a stepwise manner from large to small was fed to each extruder. Each composition was extruded in a molten state by a screw in an extruder heated to a cylinder temperature of 180 ° C. and a die temperature of 195 ° C., and then cooled by an inflation method to form a film, and the inner surface layer had the maximum conductivity. A conductive multilayer tube having a structure in which the conductivity of the surface layer is minimized was obtained. Then, it was stretched twice at 95 ° C in the circumferential direction to form a shrink tube.
The tube body has a total thickness of 150 μ (20 μ, 70 μ, 60 μ from the surface layer), an inner diameter of 15 mm, and a volume electric resistance value of 10 ⁶ Ω · cm, 10 ⁵ Ω · cm from the surface layer, 1
It was 0 ⁴ Ω · cm. This conductive multi-layer tube was cut at a length of 25 cm in a direction perpendicular to the stretching direction to produce a coating tube for a conductive roll of a copying machine. On this occasion,
The conductive roll had an outer diameter of 12 mm and had a conductive rubber layer of about 3 mm on an iron core. When a conductive roll shrink-coated with this tube is used as a charging roll and charged by a contact charging method, the roll has a small variation in resistance value, a small change in resistance due to the environment, and improved withstand voltage. It was also possible to prevent the softening agent of the sex roll from bleeding out. In addition, the printability was excellent, and clear images could be obtained even when continuous copying was performed, and the effect was exceptional.

Example 2 Of the co-extruders in which four co-extruders were equipped with annular co-extrusion dies, one of the co-extruders was a composition containing polyvinyl chloride resin as the outermost layer as a protective layer. A conductive multilayer shrink tube having an outermost layer (protective layer) was obtained in the same manner as in Example 1 except that The thickness of the tube thus obtained was 20μ, 20μ, 60μ, 60 from the outermost layer.
μ, total thickness 160 μ, volume electrical resistance from the outermost layer is 10 ⁸ Ω · cm, 10 ⁶ Ω · cm, 10 ⁵ Ω · cm,
It was 10 ⁴ Ω · cm. After cutting this conductive multilayer shrink tube in the same manner as in Example 1, a contact charging type copying machine in which a conductive roll coated with the tube as in Example 1 was considered as a charging roll was used. Even if electricity is applied, the resistance value of the charging roll varies, the change in resistance value due to the environment is small, the withstand voltage is also improved, and the bleeding out of the softening agent in the conductive rubber layer of the conductive roll can be prevented. Since it was uniformly charged, clear copies could be obtained.

Example 3 (1) The composition of the inner surface layer was 85% by weight of polyurethane resin.
And 15% by weight of Ketjen Black. (2) The composition of the intermediate layer is 63% by weight of polyurethane resin,
A compounded composition comprising 27% by weight of a composition containing a polyvinyl chloride resin as a main component and 10% by weight of Ketjenblack. (3) Composition 6 whose outer surface layer is composed of 28.5% by weight of a polyurethane resin and a polyvinyl chloride resin as a main component
A compounding composition comprising 6.5% by weight and 5% by weight of Ketjenblack. (4) A compounded composition in which the outermost layer (protective layer) is composed of 100% by weight of a composition containing a polyvinyl chloride resin as a main component. Each of the compounded compositions (1), (2), (3), and (4) described above was formed into a film on a conductive multilayer tube in the same manner as in Example 1. This conductive multi-layer tube was replaced with 25c as in Example 1.
After cutting into m, a shrink tube for coating a conductive roll was obtained. The volume electric resistance value of each layer is 10 ⁸ Ω · cm, 10 ⁶ Ω · cm, 10 ⁵ Ω · cm, 1 from the outermost layer (protective layer).
It was 0 ⁴ Ω · cm. A contact charging type copying machine equipped with a conductive roll coated with the tube as a charging roll has a small variation in the resistance value of the charging roll even if the charging roll is energized, a small change in the resistance value due to the environment, and an improved withstand voltage. In addition, bleeding out of the softening agent in the conductive roll can be prevented, and the photoconductor is uniformly charged, so clear copying is possible, and clear images can be obtained even when continuous copying is performed. Met. In this case, the shrinkage rate of the shrink tube in each example is 5% in the axial direction and 50 in the circumferential direction in the atmosphere of 120 ° C. × 3 minutes for the one of the example.
%, 5% and 50% for Example 2, and 5% and 50% for Example 3.

[0024]

The conductive multi-layer tube according to the present invention can reduce variations in resistance value in each layer and changes in electric resistance due to environment, and is expected to improve withstand voltage. Furthermore, since it is not a single-layer structure as in the past but a multilayer structure and a conductive layer containing less conductive agent as it becomes a surface layer, for example, when it is applied to a roll having a conductive elastic body layer, it is softened from the roll. It also has the effect of reducing the bleed-out of the drug.
The conductive multi-layer tube of the present invention can be used for all purposes other than roll coating of a copying machine in the future, and it can be expected to expand the applications in a wide range of fields.

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Claims (2)

[Claims] 1. At least 2 in which the content of the conductive agent in each layer containing an organic polymer material as a main component is gradually reduced from the inner surface layer to the surface layer so that the content becomes large or small. A multi-layer tube having more than one layer, wherein the inner surface layer has maximum conductivity and the surface layer has minimum conductivity. 2. The surface layer further comprises a protective layer containing an organic polymer material containing no conductive agent as a main component.
The conductive multi-layer tube according to.